1. KLASMOE, School of Mathematics and Statistics, Northeast Normal University, 5268 Ren Min Street, Chang Chun City, Ji Lin Province, China (130024)
2. School of Mathematics and Statistics, Northeast Normal University, 5268 Ren Min Street, Chang Chun City, Ji Lin Province, China (130024)
3. Department of Statistics and Applied Probability, National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077
4. Department of Economics, Hong Kong Baptist University, WLB, Shaw Campus Kowloon Tong, Hong Kong